Is #pragma once ok to use as a guard mechanism?

Hello,

sometimes I see guard mechanisms in .h files like so:

#ifndef _CLASSNAME_H_
#define _CLASSNAME_H_

...

#endif //(_CLASSNAME_H_)

doesnt "#pragma once" do the exact same thing but in one line of code? Why would anyone use the first method instead of "#pragma once" ?

Thank you,
Ellay

pragmas are not standard. -> if you want to be able to compile your code with different compilers it's better to use ordinary include guards.
kurt

Read this article:
http://en.wikipedia.org/wiki/Pragma_once